Direct contact heat exchanger and methods for making and using same

ABSTRACT

A direct heat exchange method and apparatus for recovering heat from a liquid heat source is disclosed, where the method includes contacting a liquid heat source stream with a multi-component hydrocarbon fluid, where the hydrocarbon fluid compositions has a linear or substantially linear temperature versus enthalpy relationship over the temperature range of the direct heat exchange apparatus.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of this present invention relate to a direct heat exchangemethod and apparatus for recovering heat from a liquid heat source.

Embodiments of this present invention relate to a direct heat exchangemethod and apparatus for recovering heat from a liquid heat source,where the method includes contacting a liquid heat source stream with amulti-component hydrocarbon fluid, where the hydrocarbon fluidcompositions has a linear or substantially linear temperature versusenthalpy relationship over the temperature range of the direct heatexchange apparatus.

2. Description of the Related Art

Highly mineralized geothermal brine, which is cooled in a heat recoveryprocess will, at some given temperature, start to release or precipitatesolid minerals (mostly silica). The precipitating solid materials settleout on surfaces of heat transfer equipment drastically reducing the heattransfer coefficient of the equipment. After some time, the contaminatedheat exchange equipment will become completely blocked and unworkable.

In prior art, this problem was addressed using a direct contact heatexchange apparatus. In these prior art direct contact heat exchangeapparatuses, an immiscible liquid heat transfer fluid is was broughtinto direct contact in a counter-flow relationship with the liquid heatsource. The heat transfer fluid is heated as the heat source liquid iscooled.

Because the heat source liquid and the heat transfer fluid in thisarrangement both have practically constant specific heat values, theheat recovery in this process is thermodynamically very efficient.Moreover, the heat transfer coefficients in such direct contact heatexchange apparatuses are higher than in conventional heat exchangeapparatus.

In this approach, as the heat transfer fluid and the heat source liquidmove in counter-flow, the only driving force for this movement is adifference in specific gravities of the fluids.

For purposes of heat recovery from geothermal brines, oils or liquidhydrocarbons are usually used as the heat recovery liquid.

Because the difference in the specific gravities of the heat transferfluid and the heat source fluid is usually quite small, the velocitywith which both liquids move in the direct heat exchange apparatus hasto be quite low to avoid flooding.

An alternate approach in the prior art was used by the Barber-NicholsCompany, where an Organic Rankine Cycle (ORC) working fluid (usuallyisobutane or isopentane) was vaporized in direct contact with ageothermal brine in a counter-flow relationship. However, a singlecomponent working fluid boils at a constant temperature, whereas theheat released by the geothermal brine is released at variabletemperatures or over a temperature range. Therefore, this prior artapproach, while useful for the vaporization of a single component ORCworking fluid, is not efficient for heat recovery in cases where theheat exchange fluid is then used to transfer heat to an alternateworking fluid of a power cycle (or, for that matter, to any other fluidfor other applications.)

Thus, there is a need in the art for a novel method and apparatus fordirect heat exchange from a heat source to a fluid designed to have achange enthalpy that is linear with the change in temperature along thelength of an active heat exchange zone.

SUMMARY OF THE INVENTION

Embodiments of methods of this invention include bringing a heat sourcefluid into direct contact with a multi-component heat carrier fluid in acounter-flow relationship to form a spent heat source fluid and avaporized or partially vaporized multi-component heat carrier fluid,where the fluids are immiscible and where the carrier fluid has a linearor substantially linear temperature versus enthalpy relationship over atemperature range of the direct contact heat exchange apparatus andwhere the two fluid have the same or substantially the same pressure.

Embodiments of methods of this invention including pressurizing a heatsource stream to a pressure of a multi-component heat carrier fluid. Thepressurized heat source fluid is then brought into direct contact with amulti-component heat carrier fluid in a counter-flow relationship toform a spent heat source fluid and a vaporized or partially vaporizedmulti-component heat carrier fluid, where the fluids are immiscible andwhere the carrier fluid has a linear or substantially linear temperatureversus enthalpy relationship over a temperature range of the directcontact heat exchange apparatus and where the two fluid have the same orsubstantially the same pressure. The vaporized or partially vaporizedmulti-component heat carrier fluid is then used as the heat source forheating a working fluid of a power cycle or for heating any other fluidfor use an a subsequent process.

Embodiments of this invention provide a system including a direct heatexchange subsystem, a heat exchange subsystem and heat utilizationsubsystem.

Embodiments of this invention provide a system including a direct heatexchange subsystem and a heat exchange subsystem.

Embodiments of this invention provide a heat transfer fluid having alinear or substantially linear relationship between its enthalpy andtemperature over a desired temperature range.

Embodiments of this invention provide a system including a directcontact heat exchange subsystem, a heat exchange subsystem and a heatutilization subsystem, where the heat exchange subsystem include asingle heat exchange apparatus and the direct heat exchange subsystemand the heat exchange subsystem utilize a multi-component heat carrierfluid having a linear enthalpy to temperature relationship over anoperating temperature range of the direct heat exchange apparatus.

Embodiments of this invention provide a system including a directcontact heat exchange subsystem, a heat exchange subsystem and a heatutilization subsystem, where the heat exchange subsystem includes twoheat exchange apparatuses, one adapted to cool a hot heat source streamto a temperature suitable for use with the direct heat exchangeapparatus and the direct heat exchange subsystem and the heat exchangesubsystem utilize a multi-component heat carrier fluid having a linearenthalpy to temperature relationship over an operating temperature rangeof the direct heat exchange apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the followingdetailed description together with the appended illustrative drawings inwhich like elements are numbered the same:

FIG. 1 depicts an embodiment of an integrated heat extraction and usesystem.

FIG. 2 depicts another embodiment of an integrated heat extraction anduse system.

FIG. 3 depicts an embodiment of a direct heat exchange apparatus of thisinvention.

FIG. 4 depicts another embodiment of a direct heat exchange apparatus ofthis invention.

FIG. 5 depicts a plot of several multi-component heat carrier fluidshaving a linear enthalpy to temperature relationship over a temperaturerange between about 150° F. and 260° F.

DETAILED DESCRIPTION OF THE INVENTION

The inventor has found that a method, apparatus and system can beconstructed to recover heat from a liquid heat source using a directheat transfer method and apparatus from the heat source to a systemdesigned to utilize the heat is impossible or undesirable. In certainembodiments, the method and apparatus are used to recover heat from ahighly mineralized geothermal brine so that it can be used to heat aworking fluid of a power system.

To attain efficient heat recovery from liquid heat sources with the useof boiling heat transfer fluid, the boiling of the heat transfer fluidhas to occur at variable temperature which covers the whole range of thetemperature change of the heat source liquid. Moreover, the temperaturedifference between the heat source liquid and the boiling heat transferfluid has to be maintained to be constant of close to constantthroughout the entire process.

In other words, the change in enthalpy of the boiling heat transferfluid must be linear with the change of its temperature.

The proposed invention uses a multi-component mixture of hydrocarbons asits heat transfer fluid. At least four different hydrocarbons make upthe mixture. Propane, isobutane, pentane, hexane, heptane, octane,nonane and decane can be used as components of such a mixture.

In the proposed invention, the mixture is chosen in such a way that theboiling process of the mixture presents a nearly straight line incoordinates of enthalpy vs. temperature. One experienced in the art willbe able to choose a workable combination of four or more of thesuggested components to comprise the heat transfer fluid mixture.

The multi-component heat carrying fluid mixture (or “multi-componentheat carrier,” hereafter MCHC) is used in a direct contact heatexchanger which is a vertical vessel. This can be conceptually dividedinto three parts. At the top is a space where the heated and vaporizedMCHC accumulates. In the middle is the region where the heat sourceliquid and the MCHC come into direct contact in counter-flow and theMCHC boils. At the bottom, the cooled heat source liquid and theprecipitated mineralization are collected. The bottom section of thevessel can be made of a larger diameter than the middle and top portionsof the vessel. This reduces the velocity of the brine as it settles intothe bottom and allows any MCHC that may have been carried down by thebrine to float back up.

Embodiments of the present invention utilize a multi-componenthydrocarbon fluid as a heat transfer fluid. The multi-componenthydrocarbon or multi-component heat carrier (MCHC) fluid includes amixture of at least four different hydrocarbons. Depending on an initialtemperature of the heat source fluid and a temperature profile across anactive heat exchange zone of the direct heat exchange apparatus, theexact MCHC fluid composition can vary and can be optimized for thetemperature of the heat source fluid and the a temperature profileacross an active heat exchange zone of the direct heat exchangeapparatus.

Suitable hydrocarbons for use in a MCHC fluid of this invention include,without limitation, linear or branched C1-C20 alkanes, linear orbranched C1-C20 alkenes, linear or branched C1-C20 cycloalkanes, linearor branched C1-C20 cycloalkenes, linear or branched C6-C20 aromatics,other C1-C20 hydrocarbons, where one or more carbon atoms can bereplaced by hetero atoms such as oxygen atoms and where one or morehydrogen atoms can be replaced by halogen atoms such as fluorine atoms,chlorine atoms or mixtures thereof. The hydrocarbons can also be C2-C20ethers, C3-C20 esters, C1-C20 fluorinated hydrocarbons, C1-C20chlorinated hydrocarbons, or mixtures thereof. Exemplary hydrocarbonsinclude, without limitations, ethane, propane, isopropane, butane,isobutane, pentane, isopentane, neo-pentane, linear or branched C6alkanes such as n-hexane, linear or branched C7 alkanes such asn-heptane, linear or branched C8 alkanes such as n-octane, linear orbranched C9 alkanes such as n-nonane, linear or branched C10 alkanessuch as n-decane, or linear or branched C11 alkanes such as n-undecane,linear or branched C12 alkanes such as dodecane. Exemplary aromatichydrocarbons include, without limitation, benzene, toluene, xylenes, orother aromatic hydrocarbons.

The hydrocarbon mixture is chosen in such a way that the boiling processof the mixture gives rise to a straight or substantially straight line(linear or substantially linear) relationship between enthalpy andtemperature over the temperature change of the direct heat exchangeprocess or across the direct heat exchange apparatus. One experienced inthe art will be able to choose a workable combination of four or more ofthe suggested components to comprise the heat transfer fluid mixturethat allows a substantially straight line relationship between enthalpyand temperature for a given initial temperature heat source fluid and agiven active heat exchange zone. The term substantially in the contextmeans that the relationship departs from linearity by less than or equalto 20%. In other embodiments, the term means that the relationshipdeparts from linearity by less than or equal to 15%. In otherembodiments, the term means that the relationship departs from linearityby less than or equal to 10%. In other embodiments, the term means thatthe relationship departs from linearity by less than or equal to 5%. Inother embodiments, the term means that the relationship departs fromlinearity by less than or equal to 2.5%. In other embodiments, the termmeans that the relationship departs from linearity by less than or equalto 1%.

The multi-component heat carrying fluid (or “multi-component heatcarrier” fluid, hereafter MCHC fluid) is used in a direct contact heatexchanger which is a vertical oriented vessel. The vessel can beconceptually divided into three parts: (1) a top section, region orzone, where heated and vaporized MCHC accumulates; (2) a middle section,region or zone, where the heat source liquid and the MCHC come intodirect contact in a counter-flow arrangement and components in the MCHCboil; (3) a lower section, region or zone, where the cooled heat sourceliquid accumulates, and (4) a bottom section, region or zone, wheremineral precipitate accumulates. The lower and bottom sections of thevessel can be made of a larger diameter than the middle and top sectionsof the vessel. Increasing the diameter of the lower and bottom sectionsreduces a velocity of the brine as it settles into the lower section andthe precipitate settles into the bottom section and provides additionaltime for any MCHC or component thereof that may have been carried downwith the brine to float back up into middle section.

DETAILED DESCRIPTION OF THE DRAWINGS First System Embodiment

Referring now to FIG. 1, a diagram of an embodiment of a system of thisinvention, generally 100, is shown to include a direct contact heatexchange subsystem 110, a heat exchange subsystem 160 and a heatutilization subsystem 180.

The direct contact heat exchange subsystem 110 includes a direct contactheat exchange apparatus DCHE. The apparatus DCHE includes an uppersection 112, a middle section 114, a lower section 116 and a bottomsection 118.

The middle section 114 includes a heat source inlet port 120 located atan upper portion 122 of the middle section 114 through which a pressureadjusted, heat source stream S10 having parameters as at a point 10enters the direct contact heat exchange apparatus DCHE. Because theapparatus DCHE is a constant pressure apparatus, a pressure of aninitial heat source stream S12 having parameters as at a point 12 isadjusted by passing the stream S12 through a first pump P1 to form thepressurize adjusted, heat source stream S10 having the parameters as atthe point 10. In certain embodiments, the streams S10 and S12 comprisesa highly mineralized geothermal brine, but the streams S10 and S12 canbe any heat source stream, mineralized or not. In certain embodiments,the inlet port 120 includes a sprayer or other means for dispersing thestream S10 into droplets or a spray as it enters the middle section 114of the apparatus DCHE.

Concurrently, a fully condensed, pressure adjusted multi-component heatcarrier (MCHC) fluid stream S14 having parameters as at a point 14enters the apparatus DCHE through a MCHC inlet port 124 into at a lowerportion 126 of the middle section 114 of the apparatus DCHE. Because theapparatus DCHE is a constant pressure apparatus, a pressure of a fullycondensed MCHC stream S16 having parameters as at a point 16 is adjustedby passing the stream S16 through a second and circulating pump P2 toform the fully condensed, pressurize adjusted MCHC stream S14 having theparameters as at the point 14, which is in a state of slightly subcooledliquid.

In the middle section 114 of the apparatus DCHE, the heat source streamS10 and the MCHC stream S14 directly interact. Heat from the heat sourcestream S10 heats and vaporizes or partially vaporizes the MCHC streamS14. As the MCHC stream S14 has a lower density than the heat sourcestream S10, the MCHC stream S14 will move up the middle section 114 ofthe apparatus DCHE, while the heat source stream S10 will move down themiddle section 114 of the apparatus DCHE. Of course, vaporizedcomponents of the MCHC stream S14 will rise very fast in the middlesection 114 of the apparatus DCHE. The heated and vaporized or heat andpartially vaporized MCHC stream S14 accumulates in the upper section 112of the apparatus DCHE, while the cooled heat source stream S10accumulates in the lower section 116 of the apparatus DCHE.

As the heat source stream S10 cools in contact with the MCHC stream S14in the apparatus DCHE, minerals in the heat source stream S10precipitate, but due to the configuration and design of the apparatusDCHE, the precipitate falls down through the middle section 114 of theapparatus DCHE and accumulates in the bottom section 118 due to a higherdensity of the solids. The bottom section 118 includes a solids removalport 128 through which accumulated solids can be intermittently,periodically, or continuously removed from the apparatus DCHE. Thecooled heat source fluid that accumulates in the lower section 116 ofthe apparatus DCHE is withdrawn from or leaves the apparatus DCHE via aspent heat source stream port 130 positioned in an upper portion 132 ofthe lower section 116 as a spent heat source stream S18 havingparameters as at a point 18.

A heated and fully or heated and partially vaporized MCHC stream S20having parameters as at a point 20 that has accumulated in the uppersection 112 of the apparatus DCHE is withdrawn through or leaves theapparatus DCHE via a MCHC outlet port 134 positioned at a top position136 of the upper section 112. The heated and fully or partiallyvaporized MCHC stream S20 having parameters as at the point 20 isforwarded to the heat exchange subsystem 160. In this embodiment, theheat exchange subsystem 160 includes a single heat exchange apparatusHE. The heat exchange apparatus HE can be a single stage or multi stagedheat exchanger or a single heat exchanger or a plurality of heatexchangers. In the heat exchange apparatus HE, the stream S20 havingparameters as at the point 20 is brought into a counter flow, heatexchange relationship with a fully condensed working fluid stream S22having parameters as at a point 22. Heat from the MCHC stream S20 isused to fully vaporize and in certain embodiments fully vaporize andsuperheat the working fluid stream S22. As a result of the heat exchangeprocess 20-16 or 22-24, the fully condensed MCHC stream S16 havingparameters as at a point 16 and a fully vaporized or fully vaporized andsuperheated, working fluid stream S24 having parameters as at a point 24are formed.

The MCHC stream S16 then passes through the pump P2 and into theapparatus DCHE as described above, while the fully vaporized or fullyvaporized and superheated, working fluid stream S24 is forwarded to theof the heat utilization subsystem 180. In this embodiment, the heatutilization subsystem 180 comprises a power generation system PS. Thesystem PS includes a working fluid inlet port 182 and a working fluidoutlet port 184. As the working fluid stream S24 having the parametersas at the point 24 passes through the system PS, a portion of its heatis converted into a usable form of energy producing the fully condensedworking fluid stream S22 having the parameters as at the point 22. Thepower generation subsystem PS can be any power generation subsystemknown in the art including those disclosed in U.S. Pat. Nos. 7,469,542;7,458,218; 7,458,217; 7,398,651; 7,197,876; 7,065,969; 7,065,967;7,055,326; 7,043,919; 7,021,060; 6,968,690; 6,941,757; 6,923,000;6,910,334; 6,829,895; 6,820,421; 6,769,256; 6,735,948; 6,482,272;5,953,918; 5,950,433; 5,822,990; 5,649,426; 5,572,871; 5,440,882;5,103,899; 5,095,708; 5,029,444; 4,982,568; 4,899,545; 4,763,480;4,732,005; 4,604,867; 4,586,340; 4,548,043; 4,489,563; 4,346,561;4,331,202; and United States Published Application Nos. 20080053095,20080000225, 20070234750, 20070234722, 20070068161, 20070056284, or anypatent cited therein, all of which are incorporated by operation of thelast paragraph of the detailed description.

Second System Embodiment

Referring now to FIG. 2, a diagram of an embodiment of a system of thisinvention, generally 200, is shown to include a direct contact heatexchange subsystem 210, a heat exchange subsystem 260 and a heatutilization subsystem 280.

The direct contact heat exchange subsystem 210 includes a direct contactheat exchange apparatus DCHE. The apparatus DCHE includes an uppersection 212, a middle section 214, a lower section 216 and a bottomsection 218.

The middle section 214 includes a heat source inlet port 220 located atan upper portion 222 of the middle section 214 through which a pressureadjusted, cooled heat source stream S10 having parameters as at a point10 enters the direct contact heat exchange apparatus DCHE. In thecurrent embodiment, an initial, hot heat source stream S00 havingparameter as at a point 0 is cooled as described below to from a cooledheat source stream S12 having parameters as at a point 12. Because theapparatus DCHE is a constant pressure apparatus, a pressure of thecooled heat source stream S12 having parameters as at the point 12 isadjusted by passing the stream S12 through a first pump P1 to form thepressure adjusted, cooled heat source stream S10 having the parametersas at the point 10. In certain embodiments, the streams S10, S00 and S12comprises a highly mineralized geothermal brine, but the streams S10,S00 and S12 can be any heat source stream, mineralized or not.

Concurrently, a fully condensed, pressure adjusted multi-component heatcarrier (MCHC) fluid stream S14 having parameters as at a point 14enters the apparatus DCHE through a MCHC inlet port 224 into at a lowerportion 226 of the middle section 214 of the apparatus DCHE. Because theapparatus DCHE is a constant pressure apparatus, a pressure of a fullycondensed MCHC stream S16 having parameters as at a point 16 is adjustedby passing the stream S16 through a second and circulating pump P2 toform the fully condensed, pressure adjusted MCHC stream S14 having theparameters as at the point 14, which is in a state of slightly subcooledliquid.

In the middle section 214 of the apparatus DCHE, the heat source streamS10 and the MCHC stream S14 directly interact. Heat from the heat sourcestream S10 heats and vaporizes or heats and partially vaporizes the MCHCstream S14. As the MCHC stream S14 has a lower density than the heatsource stream S10, the MCHC stream S14 will move up the middle section214 of the apparatus DCHE, while the heat source stream S10 will movedown the middle section 214 of the apparatus DCHE. Of course, vaporizedcomponents of the MCHC stream S14 will rise very fast in the middlesection 214 of the apparatus DCHE. The heated and vaporized or heatedand partially vaporized MCHC stream S14 accumulates in the upper section212 of the apparatus DCHE, while the cooled heat source stream S10accumulates in the lower section 216 of the apparatus DCHE.

For mineralized heat source streams, as the heat source stream S10 coolsin contact with the MCHC stream S14, minerals in the heat source streamS10 precipitate, but due to the configuration and design of theapparatus DCHE, the precipitate falls down through the middle section214 of the apparatus DCHE and accumulates in the bottom section 218 dueto a higher density of the solids. The bottom section 118 includes asolids removal port 228 through which accumulated solids can beintermittently, periodically, or continuously removed from the apparatusDCHE. The cooled heat source fluid that accumulates in the lower section216 of the apparatus DCHE is withdrawn from or leaves the apparatus DCHEvia a spent heat source stream port 230 positioned in an upper portion232 of the lower section 216 as a spent heat source stream S18 havingparameters as at a point 18.

A heated and fully vaporized or heated and partially vaporized MCHCstream S20 having parameters as at a point 20 that has accumulated inthe upper section 212 of the apparatus DCHE is withdrawn through orleaves the apparatus DCHE via a MCHC outlet port 234 positioned at a topposition 236 of the upper section 212. The heated and fully vaporized orheated and partially vaporized MCHC stream S20 having parameters as atthe point 20 is forwarded to the heat exchange subsystem 260. In thisembodiment, the heat exchange subsystem 260 includes a first heatexchange apparatus HE1 and a second heat exchange apparatus HE2. Theheat exchange apparatuses HE1 and HE2 can be single stage or multistaged heat exchangers or can be a single heat exchanger or a pluralityof heat exchangers. In the first heat exchange apparatus HE1, the streamS20 having parameters as at the point 20 is brought into a counter flow,heat exchange relationship with a fully condensed working fluid streamS22 having parameters as at a point 22, where heat from the MCHC streamS20 is used to heat or heat and partially vaporize the working fluidstream S22 to form the fully condensed MCHC stream S16 and a heated orheated and partially vaporized working fluid stream S26 havingparameters as at a point 26. In the second heat exchange apparatus HE2,the hot heat source stream S00 having the parameters as at the point 0is brought into a counter flow, heat exchange relationship with theheated or heated and partially vaporized S26 having the parameters 26 toform the cooled heat source stream S12 having parameters as at the point12 and a fully vaporized or vaporized and superheated, working fluidstream S24 having parameters as at a point 24.

The MCHC stream S16 then passes through the pump P2 to form the streamS14, which enters the apparatus DCHE as described above, while the fullyvaporized or fully vaporized and superheated, working fluid stream S24is forwarded to the of the heat utilization subsystem 280. In thisembodiment, the heat utilization subsystem 280 comprises a powergeneration system PS. The system PS includes a working fluid inlet port282 and a working fluid outlet port 284. As the working fluid stream S24having the parameters as at the point 24 passes through the system PS, aportion of its heat is converted into a usable form of energy producingthe working fluid stream S22 having the parameters as at the point 22.Again, the power system can be any power system as described above.

First Heat Exchange System Embodiment

Referring now to FIG. 3A, a diagram of an embodiment of a heat exchangeapparatus of this invention, generally 300, is shown to include a directheat exchange apparatus DCHE, a heat exchange apparatus HE, a heatsource pump P1 and a MCHC recirculating pump P2. The apparatus DCHEincludes an upper section 302, a middle section 304, a lower section 306and a bottom section 308. The apparatus DCHE also includes a heat sourceinlet port 310, a spent heat source outlet port 312, a MCHC inlet port314, a MCHC outlet port 316 and a solids removal port 318. The apparatusDCHE also includes a spray member 320, which breaks a fluid stream intosmall substreams or droplets 322. The heat source inlet port 310 ispositioned at an upper portion 324 of the middle section 304 of theapparatus DCHE, while the spent heat source outlet port 312 ispositioned at an upper portion 326 of the lower section 306 of theapparatus DCHE. The MCHC inlet port 314 is positioned at a lower portion328 of the middle section 304 of the apparatus DCHE, while the MCHCoutlet port 316 is positioned at a top portion 330 of the upper section302 of the apparatus DCHE.

A fully heated and fully or partially vaporized MCHC stream 51 havingparameters as at a point 1 leaves the direct contact heat exchangeapparatus DCHE and passes through the heat exchange apparatus HE. Theheat exchange apparatus HE can comprise one heat exchanger or aplurality of heat exchangers or heat exchanges with a plurality ofstages of a power system or other system that utilizes the heat.

In the apparatus HE, the MCHC stream 51 is condensed, releasing heat ofa fully condensed working fluid stream S6 having parameters as at apoint 6, and exits the apparatus HE in the form of a fully condensedliquid MCHC stream S2 with parameters as at point 2, while the workingfluid exits as a fully vaporized or fully vaporized and superheatedstream S7 having parameters as at a point 7.

The stream S2 having the parameters as at the point 2 is then sent intothe circulating pump P2, where its pressure is increased forming apressure adjusted, liquid MCHC stream S3 having parameters as at a point3, which corresponds to a state of slightly subcooled liquid. The streamS3 is then sent into the direct contact heat exchanger DCHE through theMCHC inlet port 314. The stream S3 of MCHC enters the direct contactheat exchange apparatus DCHE towards a bottom (the lower portion 328) ofthe middle section 304.

Meanwhile, heat source liquid stream S5 (e.g., a geothermal brine)having parameters as at a point 5 is sent into the pump P1, where it'spressure is increased to a pressure that matches a pressure of the MCHCfluid in the direct contact heat exchange apparatus DCHE to form apressure adjusted, heat source stream S4 having parameters as at a point4. This increase in pressure is required so that the pressure of theheat source liquid stream S4 will be equal to the pressure of the MCHCliquid stream S3, which, since it has a low boiling point, will be at apressure that is higher than the likely initial pressure of geothermalbrine, (or for that matter, of any other likely heat source liquid). Auseful side-effect of increasing the pressure of the heat source liquidS5 is that this prevents the presence of water-vapor in the directcontact heat exchange apparatus DCHE, thus avoiding considerablepossible complications.

The heat source liquid stream S4 then enters the direct contact heatexchange apparatus DCHE through the port 310 and the spray device 320 ata top (the upper portion 324) of the middle section 304 of the directcontact heat exchange apparatus DCHE. The heat source fluid stream S4 issprayed down toward the bottom of the direct contact heat exchangeapparatus DCHE.

As the heat source fluid stream S4 flows through the sprayer 320, thestream S4 is broken into multiple substreams or droplets 322 which falland sink through the MCHC stream S3 that was introduced into the directcontact heat exchange apparatus DCHE at the port 314.

These droplets of the heat source liquid stream S4 come into directcontact with the MCHC stream S3, causing components in the MCHC streamS3 to boil. Bubbles of the MCHC vapor and liquid MCHC move up throughthe direct contact heat exchange apparatus DCHE and components of theMCHC further vaporize as they move upwards, producing dry saturated MCHCvapor or wet MCHC vapor. This MCHC vapor accumulates in the top section302 of the direct contact heat exchange apparatus DCHE and leaves viathe top port 330 as the MCHC stream S1 having the parameters as at thepoint 1, which is in the state of a dry saturated or wet vapor asdescribed above.

Meanwhile, the droplets of the heat source liquid stream S4, in theprocess of cooling, release dissolved minerals. The cooled heat sourceliquid stream S4 and the precipitated minerals sink to the lower section306 and bottom sections 308 of the direct contact heat exchangeapparatus DCHE, respectively. Here, the heat source liquid S4, whichaccumulates in the lower section 306, is removed from the direct contactheat exchange apparatus DCHE via the port 312 as a spent heat sourcestream S8 having parameters as at point 8, which is in the state of asubcooled liquid. Note that the port 312 through which the spent streamS8 leaves the apparatus DCHE is positioned below the port 314 throughwhich the MCHC stream S3 enter the apparatus DCHE, so that the MCHCenters into the direct contact heat exchange apparatus DCHE above thepoint at which the heat source liquid stream S8 is removed. In this way,a level 332 of brine is always above the port 314 and thus no MCHC canexit through the brine outlet port 312.

The particles of precipitated minerals collect in the bottom section 308of the direct contact heat exchange apparatus DCHE, in the form of asludge which can be removed intermittently, periodically or continuouslythrough a trap door 318 at a very bottom of the direct contact heatexchange apparatus DCHE.

Given that heat transfer coefficients of a direct contact heat transferare very high, the temperature difference between the MCHC and the heatsource liquid is very small. Due to the linear absorption of heat by theMCHC, these temperature differences can be maintained almost at aconstant level throughout the entire process.

An additional advantage of the methods, systems and apparatuses is thatthe heat transfer (inside the heat exchange apparatus HE) from the MCHCstream S1 to the working fluid stream S6 of a power system occurs in aprocess of condensation which results in a drastic increase of theoverall heat transfer coefficient in heat exchange apparatus HE and thusreduces the required size and cost of the heat exchanger apparatus HE.

The present methods, systems and apparatuses provide for efficient heattransfer from any heat source liquid with minimum losses of energypotential. It allows the heat source liquid to be cooled to any desiredtemperature without concern for mineralization or contamination ofequipment by the heat source liquid.

Referring now to FIG. 3B, an alternate, though less efficient,embodiment of the method, system or apparatus of this invention includesa MCHC stream spray device 334 located at the bottom portion 328 of themiddle section 304 of the direct contact heat exchange apparatus DCHE.The MCHC stream S3 is sprayed up toward the top of the direct contactheat exchange apparatus DCHE. The heat source liquid stream S4 isintroduced into the direct contact heat exchange apparatus DCHE at thetop portion 324 of the middle section 304 with or without its sprayer320 and is removed at the upper portion 326 of the lower section 306 ofthe apparatus DCHE, below the port 314 through which the MCHC stream S3is introduced. This approach is less effective than the previousembodiment, but is none the less useable.

Second Heat Exchange System Embodiment

Referring now to FIG. 4, a diagram of an embodiment of a heat exchangeapparatus of this invention, generally 400, is shown to include a directheat exchange apparatus DCHE, a heat exchange apparatus HE, a heatsource pump P1 and a MCHC recirculating pump P2. The apparatus DCHEincludes an upper section 402, a middle section 404, a lower section 406and a bottom section 408. The apparatus DCHE also includes a heat sourceinlet port 410, a spent heat source outlet port 412, a MCHC inlet port414, a MCHC outlet port 416 and a solids removal port 418. The apparatusDCHE also includes a spray member 420, which breaks a fluid stream intosmall substreams or droplets 422. The heat source inlet port 410 ispositioned at an upper portion 424 of the middle section 404 of theapparatus DCHE, while the spent heat source outlet port 412 and sprayer420 are positioned at an upper portion 426 of the lower section 406 ofthe apparatus DCHE. The MCHC inlet port 414 is positioned at a lowerportion 428 of the middle section 404 of the apparatus DCHE, while theMCHC outlet port 416 is positioned at a top portion 430 of the uppersection 402 of the apparatus DCHE.

A heated and fully vaporized or heated and partially vaporized MCHCstream 51 having parameters as at the point 1 is withdrawn from the port416 of the apparatus DCHE and forwarded to the a first heat exchangeapparatus HE1. In the first heat exchange apparatus HE1, the stream 51having parameters as at the point 1 is brought into a counter flow, heatexchange relationship with a fully condensed working fluid stream S6having parameters as at a point 6. Heat from the MCHC stream 51 is usedto heat or heat and partially vaporize the working fluid stream S6 toform a fully condensed MCHC stream S2 having parameters as at a point 2and a heated or heated and partially vaporized working fluid stream S7having parameters as at a point 7.

The MCHC stream S2 having the parameters as at the point 2 is then sentinto the recirculating pump P2, where its pressure is increased forminga pressure adjusted, liquid MCHC stream S3 having parameters as at apoint 3, which corresponds to a state of slightly subcooled liquid. Thestream S3 is then sent into the direct contact heat exchanger DCHEthrough the MCHC inlet port 414. The stream S3 of MCHC enters the directcontact heat exchange apparatus DCHE towards a bottom (the lower portion428) of the middle section 404.

Meanwhile, in a second heat exchange apparatus HE2, a hot heat sourcestream S00 having the parameters as at a point 0 is brought into acounter flow, heat exchange relationship with the heated or heated andpartially vaporized S7 having the parameters as at the point 7 to form acooled heat source stream S5 having parameters as at a point 5 and afully vaporized or fully vaporized and superheated, working fluid streamS9 having parameters as at a point 9. The heat exchange apparatuses HE1and HE2 can be single stage or multi staged heat exchangers or can be asingle heat exchanger or a plurality of heat exchangers.

The heat source liquid stream S5 (e.g., a geothermal brine) havingparameters as at the point 5 is sent into the pump P1, where it'spressure is increased to a pressure that matches a pressure of the MCHCfluid stream S3 in the direct contact heat exchange apparatus DCHE toform a pressure adjusted, heat source stream S4 having parameters as ata point 4. This increase in pressure is required so that the pressure ofthe heat source liquid will be equal to the pressure of the MCHC liquid,which, since it has a low boiling point, will be at a pressure that ishigher than the likely initial pressure of geothermal brine, (or forthat matter, of any other likely heat source liquid). A usefulside-effect of increasing the pressure of the heat source liquid is thatthis prevents the presence of water-vapor in the direct contact heatexchange apparatus DCHE, thus avoiding considerable possiblecomplications.

The heat source liquid stream S4 then enters the direct contact heatexchange apparatus DCHE through the spray device 420 at a top (the upperportion 424) of the middle section 404 of the direct contact heatexchange apparatus DCHE. The heat source fluid is sprayed down towardthe bottom of the direct contact heat exchange apparatus DCHE.

As the heat source fluid stream S4 flows through the sprayer 420, thestream S4 is broken into multiple droplets or substreams 422 which falland sink through the MCHC stream S3 having the parameters as at thepoint 3 that was introduced into the direct contact heat exchangeapparatus DCHE at the port 414.

These droplets 422 of the heat source liquid stream S4 come into directcontact with the MCHC stream S3, causing components in the MCHC streamS3 to boil. Bubbles of the MCHC vapor and liquid MCHC move up throughthe direct contact heat exchange apparatus DCHE and components of theMCHD further vaporize as they move upwards, producing dry saturated MCHCvapor or wet MCHC vapor. This MCHC vapor accumulates in the top section402 of the direct contact heat exchange apparatus DCHE and leaves viathe top port 416 as the MCHC stream S1 having the parameters as at thepoint 1, in the state of a dry saturated or wet vapor as describedabove.

Meanwhile, the droplets of the heat source liquid stream S4, in theprocess of cooling, release dissolved minerals. The cooled heat sourceliquid stream S4 and the precipitated minerals sink to the lower section406 and bottom sections 408 of the direct contact heat exchangeapparatus DCHE. Here, the heat source liquid, which accumulates in thelower section 406, is removed from the direct contact heat exchangeapparatus DCHE via the port 412 as a spent heat source stream S8 havingparameters as at point 8, which is in the state of a subcooled liquid.Note that the port 412 through which the spent stream S8 leaves theapparatus DCHE is positioned below the port 414 through which the MCHCstream S3 enter the apparatus DCHE, so that the MCHC enters into thedirect contact heat exchange apparatus DCHE above the point at which theheat source liquid stream S8 is removed. In this way, a level 432 of thebrine is always above the port 414 and thus no MCHC can exit through thebrine outlet port 412.

The particles of precipitated minerals collect at the bottom section 308of the direct contact heat exchange apparatus DCHE, in the form of asludge which can be removed intermittently, periodically or continuouslythrough a trap door 318 at a very bottom of the direct contact heatexchange apparatus DCHE.

Given that heat transfer coefficients of a direct contact heat transferare very high, the temperature difference between the MCHC and the heatsource liquid is very small. Due to the linear absorption of heat by theMCHC, these temperature differences can be maintained almost at aconstant level throughout the entire process.

A characteristic of the method, system and apparatus of this inventionis that the heat transfer (inside of the apparatus HE1) from the MCHC tothe working fluid of a power system occurs in the process ofcondensation, which results in a drastic increase of the overall heattransfer coefficient in the apparatus HE1 and thus reduces the requiredsize and cost of the heat exchanger apparatus that makes up theapparatus HE1.

The systems of this invention provide for efficient heat transfer fromany heat source liquid with minimum losses of energy potential. Itallows the heat source liquid to be cooled to any desired temperaturewithout concern for mineralization or contamination of equipment by theheat source liquid.

An alternate, though less efficient embodiment of the proposed systemcan be designed so that the MCHC is sent in to the direct contact heatexchanger through a spray device at the bottom of the middle section ofthe direct contact heat exchanger. The MCHC is sprayed up toward the topof the direct contact heat exchanger. Heat source liquid is introducedinto the direct contact heat exchanger at the top of the middle sectionand is removed at the bottom, below the point at which the MCHC isintroduced. This approach is less effective than the preferredembodiment of the proposed invention, but is none the less useable.

A graph of the process of heat exchange between the heat transfer fluidand the heat source fluid is given in FIG. 5. For FIG. 5, the MCHC fluidcomprised, by weight, 0.2 isobutane, 0.3 pentane, 0.35 hexane and 0.25octane, for a weight ratio of isobutane:pentane:hexane:octane of2:3:3.5:2.5. The pressure of the MCHC was 60 psi at the boiling pointand 57 psi at the dew point. While these composition was constructed toproduce a fluid have a linear enthalpy versus temperature relationshipover the temperature range of about 150° F. to about 260° F. One ofordinary skill in the art can construct a suitable mixture of solvent orfluids that have a linear enthalpy to temperature relationship over agiven temperature range. The boiling points for isobutane, pentane,hexane and octane are 11° F., 97° F., 156° F. and 258° F. If you wantedto lower the temperature range you could substitute heptane, boilingpoint 209° F. If you wanted to raise the temperature range, you couldbutane, boiling point 40° F., isohexane, boiling 140.5° F., isooactane,boiling point 211° F., or heptane, boiling point 209° F., and nonane,boiling point 313° F. The weight ratios will generally range between1:1:1:1 to about 1:1.5:2:1.5, however, other weight ratios are possibledepending on the compounds used and on the temperature range desired. Ofcourse, as is clearly set forth in the embodiments of FIG. 2 and FIG. 4,if the heat source fluid is outside the temperature, i.e., is too hot,the temperature of the fluid can be reduced by first passing the streamthrough a traditional heat exchanger, provided that the temperature isnot reduced below the precipitation temperature of the heat sourcefluid.

All references cited herein are incorporated by reference. Although theinvention has been disclosed with reference to its preferredembodiments, from reading this description those of skill in the art mayappreciate changes and modification that may be made which do not departfrom the scope and spirit of the invention as described above andclaimed hereafter.

1. A system comprising: a direct contact heat exchange subsystemincluding at least one direct heat exchange apparatus, and a heatexchange subsystem, where the direct heat exchange apparatus and theheat exchange apparatus utilize a multi-component heat carrier (MCHC)fluid having a linear enthalpy to temperature relationship over anoperating temperature range of the direct heat exchange apparatus. and2. The system of claim 1, further comprising: a heat utilizationsubsystem adapted to convert a portion of heat from a working fluid to ausable form of energy.
 3. The system of claim 1, wherein the MCHC fluidcomprises at least four components mixed in a weight ratio having linearenthalpy to temperature relationship over an operating temperature rangeof the direct heat exchange apparatus.
 4. The system of claim 1, whereinthe heat exchange subsystem includes a single heat transfer apparatus.5. The system of claim 4, wherein the heat exchange apparatus comprisesa single heat exchanger, a plurality of heat exchangers, or amulti-stage heat exchanger.
 6. The system of claim 1, wherein the heatsource fluid and the multi-component heat carrier fluid are pressureadjusted so that they have the same pressure in the direct heat exchangeapparatus.
 7. The system of claim 1, further comprising: a heat sourcepump and a multi-component heat carrier fluid pump, where the heatsource pump raise a pressure of the heat source fluid to a pressureequal to a pressure multi-component heat carrier fluid over theoperating temperature of the direct heat exchange apparatus.
 8. Thesystem of claim 1, wherein the direct heat exchange apparatus includesan upper section, a middle section, a lower section and a bottom sectionadapted to accumulated mineral precipitates.
 9. The system of claim 8,further including a a MCHC fluid inlet port located in a lower portionof the middle section of the direct heat exchange apparatus, a MCHCfluid oulet port located in a top portion of the upper section of thedirect heat exchange apparatus, a heat source fluid inlet port locatedin an upper portion of the middle section of the direct heat exchangeapparatus, a heat source fluid outlet port located in an upper portionof the lower section of the direct heat exchange apparatus, and amineral precipitate port located at a bottom of the bottom section ofthe direct heat exchange apparatus for intermittent, periodic orcontinuous removal of mineral precipitate from the bottom section of thedirect heat exchange apparatus, where the MCHC inlet port is disposedabove the heat source outlet so that no or substantially no MCHC isremoved from the direct heat exchange apparatus as it exits.
 10. Thesystem of claim 9, wherein the heat source inlet port includes a sprayerfor breaking the heat source fluid into droplets or jets.
 11. The systemof claim 1, wherein heat exchange subsystem including two heat transferapparatuses, where one of the heat exchange apparatuses is adapted tocool a hot heat source stream to a temperature suitable for use in thedirect heat exchange apparatus and the direct heat exchange subsystemand the heat exchange subsystem utilize a multi-component heat carrierfluid having a linear enthalpy to temperature relationship over anoperating temperature range of the direct heat exchange apparatus.
 12. Amethod comprising: pressurizing a heat source stream to a pressure equalto a pressure to a multi-component heat carrier (MCHC) fluid to form apressure, adjusted heat source stream, forwarding the pressure, adjustedheat source stream to a heat source inlet port of a direct heat exchangeapparatus located in an upper portion of a middle section of the directheat exchange apparatus, concurrently, forwarding a pressure adjusted,fully condensed multi-component heat carrier (MCHC) stream to a MCHCinlet port of the direct heat exchange apparatus located at a lowerportion of the middle section of the direct heat exchange apparatus,where the MCHC fluid has a lower density than the heat source stream,exchanging heat between the heat source stream and the MCHC stream inthe direct heat exchange apparatus as the MCHC fluid rises in the directheat exchange apparatus and the heat source stream falls in the directheat exchange apparatus, accumulating a MCHC saturated vapor or a MCHCpartially vaporized fluid in an upper section of the direct heatexchange apparatus, accumulating the cooled heat source fluid in a lowersection of the direct heat exchange apparatus, accumulating a mineralprecipitate in a bottom section of the direct heat exchange apparatus,withdrawing a spent heat source stream from the lower section of thedirect heat exchange apparatus via a heat source outlet port located inan upper portion of the lower section of the direct heat exchangeapparatus below the MCHC inlet, withdrawing the saturated MCHC vaporfrom the direct heat exchange apparatus as a MCHC saturated vapor streamor a partially vaporized MCHC stream via a MCHC outlet port located in atop portion of the upper section of the direct heat exchange apparatus,passing the MCHC saturated vapor stream or a partially vaporized MCHCstream through a heat exchange apparatus in counter-flow with a fullycondensed working fluid stream to form a fully condensed MCHC stream anda fully vaporized or fully vaporized and superheated working fluidstream, and passing the fully condensed MCHC stream through acirculating pump to adjust the pressure of the stream to an entrypressure to form the pressure adjusted, fully condensed MCHC stream. 13.The method of claim 12, further comprising: converting a portion of theheat in the fully vaporized or fully vaporized and superheated workingfluid stream into a usable form of energy in an energy extractionsubsystem.
 14. The method of claim 12, wherein the MCHC fluid comprisesat least four components mixed in a weight ratio having linear enthalpyto temperature relationship over an operating temperature range of thedirect heat exchange apparatus.
 15. The system of claim 12, wherein theheat source inlet port includes a sprayer for breaking the heat sourcefluid into droplets or jets and wherein the heat exchange apparatuscomprises a single heat exchanger, a plurality of heat exchangers, or amulti-stage heat exchanger.
 16. A method comprising: passing a hot heatsource stream through a first heat exchange apparatus in counter flowheat exchange relationship with a heated or heated and partiallyvaporized working fluid stream to form a fully vaporized or fullyvaporized and superheated working fluid stream and a cooled heat sourcestream, pressurizing the cooled heat source stream to a pressure equalto a pressure to a multi-component heat carrier (MCHC) fluid to form apressure, adjusted cooled heat source stream, forwarding the pressure,adjusted heat source stream to a heat source inlet port of a direct heatexchange apparatus located in an upper portion of a middle section ofthe direct heat exchange apparatus, concurrently, forwarding a pressureadjusted, fully condensed multi-component heat carrier (MCHC) stream toa MCHC inlet port of the direct heat exchange apparatus located at alower portion of the middle section of the direct heat exchangeapparatus, where the MCHC fluid has a lower density than the heat sourcestream, exchanging heat between the heat source stream and the MCHCstream in the direct heat exchange apparatus as the MCHC fluid rises inthe direct heat exchange apparatus and the heat source stream falls inthe direct heat exchange apparatus, accumulating a MCHC saturated vaporor a MCHC partially vaporized fluid in an upper section of the directheat exchange apparatus, accumulating the cooled heat source fluid in alower section of the direct heat exchange apparatus, accumulating amineral precipitate in a bottom section of the direct heat exchangeapparatus, withdrawing a spent heat source stream from the lower sectionof the direct heat exchange apparatus via a heat source outlet portlocated in an upper portion of the lower section of the direct heatexchange apparatus below the MCHC inlet, withdrawing the saturated MCHCvapor from the direct heat exchange apparatus as a MCHC saturated vaporstream or a partially vaporized MCHC stream via a MCHC outlet portlocated in a top portion of the upper section of the direct heatexchange apparatus, passing the MCHC saturated vapor stream or apartially vaporized MCHC stream through a second heat exchange apparatusin counter-flow with a fully condensed working fluid stream to form afully condensed MCHC stream and a heated or heated and partiallyvaporized working fluid stream, and passing the fully condensed MCHCstream through a circulating pump to adjust the pressure of the streamto an entry pressure to form the pressure adjusted, fully condensed MCHCstream.
 17. The method of claim 16, further comprising: converting aportion of the heat in the fully vaporized or fully vaporized andsuperheated working fluid stream into a usable form of energy in anenergy extraction subsystem.
 18. The method of claim 16, wherein theMCHC fluid comprises at least four components mixed in a weight ratiohaving linear enthalpy to temperature relationship over an operatingtemperature range of the direct heat exchange apparatus.
 19. The systemof claim 12, wherein the heat source inlet port includes a sprayer forbreaking the heat source fluid into droplets or jets.
 20. The system ofclaim 12, wherein the heat exchange apparatuses comprise a single heatexchanger, a plurality of heat exchangers, or a multi-stage heatexchanger.